A 14-year-old girl and a 15-year-old boy are in hospital after being stabbed, police have said.
An armed response unit was sent to Whitefield Drive in Westvale, Kirkby, at 20:25 BST, Merseyside Police said.
The force said the road was closed at the junction with Harriers Crescent, and urged people to avoid the area.
Det Ch Insp Cath Cummings said: "We understand the concern that such a serious incident will cause in our communities, especially given the young age of the victims.
She added: "I'd ask that anyone who saw the incident, was passing, or lives nearby, shares what they know so we can establish what happened and find those responsible.
"There will be a significant police presence in the area tonight.
"If you know anything, do the right thing and come forward."
